Provide Chunk Coordinates as a Long API

Allows you to easily access the chunks X/z as a long, and a method
to look up by the long key too.

paper-api/src/main/java/org/bukkit/Chunk.java

@@ -36,6 +36,32 @@ public interface Chunk extends PersistentDataHolder {
      */
     int getZ();
 
+    // Paper start
+    /**
+     * @return The Chunks X and Z coordinates packed into a long
+     */
+    default long getChunkKey() {
+        return getChunkKey(getX(), getZ());
+    }
+
+    /**
+     * @param loc Location to get chunk key
+     * @return Location's chunk coordinates packed into a long
+     */
+    static long getChunkKey(@NotNull Location loc) {
+        return getChunkKey((int) Math.floor(loc.getX()) >> 4, (int) Math.floor(loc.getZ()) >> 4);
+    }
+
+    /**
+     * @param x X Coordinate
+     * @param z Z Coordinate
+     * @return Chunk coordinates packed into a long
+     */
+    static long getChunkKey(int x, int z) {
+        return (long) x & 0xffffffffL | ((long) z & 0xffffffffL) << 32;
+    }
+    // Paper end
+
     /**
      * Gets the world containing this chunk
      *